Abstract

A considerable amount of research has claimed that animals’ foraging behaviors display movement lengths with power-law
distributed tails, characteristic of Le
́
vy flights and Le
́
vy walks. Though these claims have recently come into question, the
proposal that many animals forage using Le
́
vy processes nonetheless remains. A Le
́
vy process does not consider when or
where resources are encountered, and samples movement lengths independently of past experience. However, Le
́
vy
processes too have come into question based on the observation that in patchy resource environments resource-sensitive
foraging strategies, like area-restricted search, perform better than Le
́
vy flights yet can still generate heavy-tailed
distributions of movement lengths. To investigate these questions further, we tracked humans as they searched for hidden
resources in an open-field virtual environment, with either patchy or dispersed resource distributions. Supporting previous
research, for both conditions logarithmic binning methods were consistent with Le
́
vy flights and rank-frequency methods–
comparing alternative distributions using maximum likelihood methods–showed the strongest support for bounded
power-law distributions (truncated Le
́
vy flights). However, goodness-of-fit tests found that even bounded power-law
distributions only accurately characterized movement behavior for 4 (out of 32) participants. Moreover, paths in the patchy
environment (but not the dispersed environment) showed a transition to intensive search following resource encounters,
characteristic of area-restricted search. Transferring paths between environments revealed that paths generated in the
patchy environment were adapted to that environment. Our results suggest that though power-law distributions do not
accurately reflect human search, Le
́
vy processes may still describe movement in dispersed environments, but not in patchy
environments–where search was area-restricted. Furthermore, our results indicate that search strategies cannot be inferred
without knowing how organisms respond to resources–as both patched and dispersed conditions led to similar Le
́
vy-like
movement distributions